1. Field of the Invention
This invention is related to wellbore packers and methods of their use; in certain particular aspects, to an hydraulically set wellbore straddle pack-off system and methods of its use; and in one particular aspect to such a system that is set and released without mechanically pulling or pushing on the system.
2. Description of Related Art
Often in wellbore operations it is desirable to "straddle" an area of interest in a wellbore, e.g. a formation or part thereof or a zone or location in a wellbore packing off the wellbore above and below the area of interest. Typically a packer is set above and another packer is set below the area of interest.
A variety of prior art straddle pack-off tools are available which include two selectively-settable spaced-apart packing elements. Several such prior art tools use a piston or pistons movable in response to hydraulic pressure to actuate packer element setting apparatus. Debris or other material can block or clog the piston apparatus, inhibiting or preventing setting of the packer elements (and preventing un-setting/release of the packer elements.
Various prior art tools have no emergency pressure release feature, useful, e.g. when a formation goes to vacuum.
Many prior art pack-off systems require the application of tension and/or compression to parts of the system (mechanical pulling and/or pushing), to actuate parts of the system. Such systems cannot be used on coiled tubing.
There has long been a need for an efficient and effective wellbore straddle pack-off system. There has long been a need for such a system without a piston that could be clogged by debris. There has long been a need for such a system which can be selectively released in an emergency situation. There has long been a need for such a system which does not require pulling or pushing for actuation. There has long been a need for such a system useful on coiled tubing.